Garmin Tunnel Mode

 

Anyone know how Garmin Tunnel Mode works? I thought it might be Dead Reckoning, but my speed in the tunnel changed and the speedometer on the GPS unit did not. I have a Drive Assist 50 if that matters. Just curious how it worked.

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The navigator knows a tunnel is present and you entered it. It assumes you keep the same speed until it calculates that you should have emerged from the length of the tunnel at that speed. If the expected time elapses and the signal is not reacquired, you will see the signal lost error message.

That Reads like Dead Reckoning

WuLabsWuTecH wrote:

Anyone know how Garmin Tunnel Mode works? I thought it might be Dead Reckoning, but my speed in the tunnel changed and the speedometer on the GPS unit did not. I have a Drive Assist 50 if that matters. Just curious how it worked.

That you stated the GPS indicated speed did not change is a very strong indicator that the device is doing dead reckoning. The GPS device latches the last known speed and uses that until it regains satellite signal.

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When you are dead, you don’t know that you are dead. It is only difficult for the others. It is the same when you are stupid.
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